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Abstract

In the title compound, {[Cd(C9H4N2O4)(C3H7NO)(H2O)]·2H2O}n, the CdII atom is coordinated by one N atom and three O atoms from four different 1H-benzimidazole-5,6-dicarboxyl­ate (Hbidc) ligands, one O atom from one dimethyl­formamide ligand, and one O atom from a water mol­ecule in a distorted octa­hedral geometry. The Hbidc ligands connect the Cd atoms into a two-dimensional network parallel to (001). N—HO and O—HO hydrogen bonds involving the water molecules are observed in the crystal structure.

Acknowledgments

The authors acknowledge Guang Dong Ocean University for supporting this work.

supplementary crystallographic
information

Comment

From the structural point of view,
1H-benzimidazole-5,6-dicarboxylic acid (H3bidc)
possesses two N atoms of imidazole ring and four O atoms of
carboxylate groups and might be used as versatile linker in constructing
coordination polymers with abundant hydrogen bonds. Based on this idea,
a series of coordination polymers fomed by this ligand
have been reported by us:
catena-poly[[diaqua(1,10-phenanthroline-κ2N,N')nickel(II)]-
µ-Hbidc-κ2N3:O6] (Song, Wang, Hu et al., 2009),
pentaaqua(Hbidc-κN3)cobalt(II) pentahydrate
(Song, Wang, Li et al., 2009),
pentaaqua(Hbidc-κN3)nickel(II) pentahydrate
(Song, Wang, Qin et al., 2009), and
tetraaquabis(Hbidc-κN3)cobalt(II) dimethylformamide disolvate dihydrate
(Wang et al., 2009). In the present paper,
we report the title complex.

As shown in Fig. 1, the CdII atom exhibits an octahedral coordination
geometry, defined by three O atoms from three different Hbidc ligands,
one N atom from another Hbidc ligand, one O atom from
a dimethylformamide ligand and one O atom from a water molecule.
The equatorial plane is defined by O1W, O10,
N1i and O3iii atoms, while O1 and O4ii occupy the axial positions
[symmetry codes: (i) -x, 1-y, 1-z;
(ii) 1+x, y, z;
(iii) -x, -y, 1-z].
Two solvent water molecules are present in the asymmetic unit.
O—H···O and N—H···O hydrogen bonds are
observed in the crystal structure with hydrogen-bond geometry
in the normal range (Fig. 2 and Table 1).

Experimental

A dimethylformamide solution (20 ml) containing CdCl2(0.1 mmol) and
H3bidc (0.2 mmol) was stirred for a few
minutes in air, and then left to stand at room temperature.
Colorless crystals were obtained in a few weeks.

Refinement

C- and N-bound H atoms were placed at calculated positions and
treated as riding on the parent atoms, with C—H = 0.93 (CH), 0.96 (CH3),
N—H = 0.86 Å and with Uiso(H) =
1.2(1.5 for methyl)Ueq(C, N).
The water H-atoms were located in a difference Fourier map and
refined as riding, with a distance
restraint of O—H = 0.84 Å and with
Uiso(H) = 1.5Ueq(O).
The highest residual electron density was found 1.07 Å from Cd1
and the deepest hole 0.97 Å from Cd1.